Text on button is not visible in Window QML Type when dark mode is enabled on macOS

Steps to reproduce:

1. Build and run the attached sample project on macOS
2. Enable dark mode in the system setting.
3. Click on the app windows to make it active

Expected: Text on the button should always be visible

Actual: Text is visible only when the app is out of focus, when the window of the app is active the text is not visible. It does not happen with ApplicationWindow, it is reproducible with Window type. See attached video. 

Reproducibility:  100%